The present invention relates in general to an improved differential drive assembly. More particularly, the present invention relates to an improved differential drive assembly which differentially transfers rotational power from a drive member to output shafts on either side thereof without the use of differential gears.
Differential drive assemblies, or more simply mechanical differentials, are utilized in many applications in which it is desired to allow a common rotational input to be differentially transferred between two rotational outputs. For example, a "differential" may be placed between the rear wheels of a rear wheel drive automobile to differentially transfer rotational power from the vehicle's drive shaft to each of the two rear axles.
One type of differential used for this purpose is commonly referred to as a "gear-type" differential. Gear-type differentials are generally very efficient on surfaces that provide good traction, such as pavement or dry dirt. They are not, however, particularly efficient on surfaces that provide poor traction, such as snow, ice or mud. If one wheel loses traction and begins to spin freely, all drive motion is lost through the spinning wheel. In this case, the vehicle may become immobilized due to the lack of traction of the spinning wheel (even though the nonslipping wheel may have sufficient traction). Because substantially all of the driving motion from the drive shaft is transferred to the spinning wheel, the other wheel will generally not receive sufficient rotational power to mobilize the vehicle.
Another type of differential, commonly referred to as a limited slip or positive traction differential, is a modification of the gear-type differential. Small clutches are typically placed outboard of each differential gear to provide some degree of binding between the differential gear and the associated output shaft. Differentials of this type, however, have often not transferred sufficient power to a tractional wheel to prevent a vehicle from becoming immobilized. Additionally, the binding caused by this construction may contribute to tire tread wear.